Hyperscanning is a quite recent paradigm in neuroscience which consists in the
simultaneous recording of the cerebral activity of two or more subjects involved in
interactive tasks. This measure allows to explore inter-personal brain mechanisms
underlying and generated by social interactions, when participants are continuously
modifying their own actions according to the partner’s ones. Previous studies showed
that this mutual adaptation results in interactional brain synchrony to which all
members contribute; accordingly, these mechanisms are involved only during interactive
social relations and cannot be captured by conventional single-subject recordings.
However, hyperscanning research recurred to either electrocortical or imaging
techniques to explore the temporal dynamics or the brain networks involved in interactive
behaviors but, to our knowledge, there are no previous attempts to acquire
both measures jointly. Thus, the aim of the present study was to investigate the cognitive
processes underlying the execution of joint cooperative actions performed by
couples of subjects by means of a multi-method hyperscanning technique. We aimed
at assessing to what extent cortical synchronization, in both electrophysiological
(by EEG) and hemodynamic (by fNIRS) components, could emerge between two
brains during cooperation. Also, we intended to explore arousal-related peripheral
responses during the task. To explore these issues, 14 participants paired as 7 dyads
were recorded with dual-EEG and dual-fNIRS setups while they were engaged in an
attentive task finalized to engage cooperation. After a resting period which served as
control condition, the task was sub-divided in 8 blocks with a pause halfway assessing
the goodness of the cooperation scores. Thus, inter-brain activity coherence over
the prefrontal regions was calculated between the two participants across blocks. We
found that the coherence between the two signals varied across blocks in accordance
to the perceived degree of cooperation. Such differences point toward a modulation
between the two subjects’ brain activity as a function of the task, with respect to control
conditions. This work represents the first use of dual-EEG/dual-fNIRS setups
for simultaneous measurements of brain-to-brain coupling and endorses the use of
hyperscanning techniques for social interactive studies in naturalistic environments.

Hyperscanning is a quite recent paradigm in neuroscience which consists in the
simultaneous recording of the cerebral activity of two or more subjects involved in
interactive tasks. This measure allows to explore inter-personal brain mechanisms
underlying and generated by social interactions, when participants are continuously
modifying their own actions according to the partner’s ones. Previous studies showed
that this mutual adaptation results in interactional brain synchrony to which all
members contribute; accordingly, these mechanisms are involved only during interactive
social relations and cannot be captured by conventional single-subject recordings.
However, hyperscanning research recurred to either electrocortical or imaging
techniques to explore the temporal dynamics or the brain networks involved in interactive
behaviors but, to our knowledge, there are no previous attempts to acquire
both measures jointly. Thus, the aim of the present study was to investigate the cognitive
processes underlying the execution of joint cooperative actions performed by
couples of subjects by means of a multi-method hyperscanning technique. We aimed
at assessing to what extent cortical synchronization, in both electrophysiological
(by EEG) and hemodynamic (by fNIRS) components, could emerge between two
brains during cooperation. Also, we intended to explore arousal-related peripheral
responses during the task. To explore these issues, 14 participants paired as 7 dyads
were recorded with dual-EEG and dual-fNIRS setups while they were engaged in an
attentive task finalized to engage cooperation. After a resting period which served as
control condition, the task was sub-divided in 8 blocks with a pause halfway assessing
the goodness of the cooperation scores. Thus, inter-brain activity coherence over
the prefrontal regions was calculated between the two participants across blocks. We
found that the coherence between the two signals varied across blocks in accordance
to the perceived degree of cooperation. Such differences point toward a modulation
between the two subjects’ brain activity as a function of the task, with respect to control
conditions. This work represents the first use of dual-EEG/dual-fNIRS setups
for simultaneous measurements of brain-to-brain coupling and endorses the use of
hyperscanning techniques for social interactive studies in naturalistic environments.